The CZ (Czochralski) method is a crystal growth method that grows a silicon single crystal by retaining a melt in a crucible in a pulling furnace and pulling the silicon single crystal from the melt by pulling mechanism.
In order to obtain a silicon single crystal having n-type electrical characteristics, a dopant such as arsenic, red phosphorus, or antimony must be added to the silicon single crystal. As a method for adding these dopants to a silicon crystal, a method of lowering a sample chamber housing a sublimable dopant down to a predetermined position above a melt in a pulling furnace, heating and subliming a sublimable dopant by radiation heat from the melt, and introducing the sublimable dopant, which is sublimed to a gaseous form, into the melt has been adopted.
As a method for introducing the dopant in the gaseous form to the melt, a method is cited, in which an open end of a supply pipe is disposed above a melt and the dopant carried by carrier gas composed of inert gas such as argon gas is sprayed from the supply pipe toward the melt, as shown in Patent Documents 1 and 2. As another method, a method is cited in which a supply pipe is dipped in a melt and a dopant that is sublimed to a gaseous form is input into the melt through the supply pipe.
Patent Document 1 discloses an invention of pulling and growing a silicon single crystal ingot having a different specific resistance range discontinuously in a direction of growth, by: disposing a doping tube at a position not interfering with a pulling mechanism; lowering the doping tube down to a position above an upper face of a quartz crucible; melting a dopant inside a housing container by radiation heat from the melt at the position; and then lowering the housing container to a position so as to be dipped in the melt and thereby adding the melted dopant to the melt from an open surface of the doping tube.
Patent Document 2 discloses an invention of a supply pipe assembly, in which a granular dopant is input into a sealed room having an open upper end portion of a supply tube in the center thereof, the dopant is vaporized by dipping an open lower end portion of the supply pipe in a silicon melt, thereby introducing the dopant into the melt using pressure of the dopant.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2005-336020
[Patent Document 2]
Japanese Unexamined Patent Application (Translation of PCT Application), Publication No. 2003-532611